Enzyme-Responsive Hemostatic Elastin-like Polypeptides for Fibrin Stabilization and Coagulation Restoration in Thrombocytopenia.

Hemorrhage remains a leading cause of mortality in trauma and surgery, and treatment options are limited for thrombocytopenic patients with impaired platelet function. Current plasma-derived hemostatic products face challenges, including limited supply, storage requirements, and infectious risk. Here we report a recombinant protein-based hemostat designed to enhance clot mechanics through enzyme responsiveness and self-assembly, which integrates biophysical design principles with clot-targeted drug delivery. We rationally designed a library of enzyme-responsive glutamine (Q)-containing block elastin-like polypeptides (Q-block-ELPs) that reinforce fibrin clots through phase separation and covalent cross-linking. Q-block-ELPs incorporate glutamine residues within a peptide motif recognized by coagulation factor XIIIa, enabling site-specific grafting into fibrin networks during clot formation. By tuning polymer length, Q-block valency, and lower critical solution temperature (LCST) behavior, we engineered Q-block-ELPs to phase separate at body temperature and integrate into the fibrin architecture. In vitro, Q-block-ELPs increase fibrin network density and stiffness. In a thrombocytopenic mouse model, systemic administration reduced blood loss and accelerated clot formation. This strategy delivers a programmable, pathogen-free platform for systemic bleeding control, bridging biophysical protein design with translational hemostatic therapy, and addressing an urgent need for platelet-deficient bleeding disorders.